Method for placing contact on electrical connector

Abstract

Electrical connectors capable of being mounted on circuit substrates by BGA techniques and a method for manufacturing such connectors. There is at least one recess on the exterior side of the connector elements. A conductive contact extends from adjacent the interior side of the into the recess on the exterior side of the housing. A controlled volume of solder paste is introduced into the recess. A fusible conductive element, in the form of solder balls is positioned in the recess. The connector is subjected to a reflow process to fuse the solder ball to the portion of the contact extending into the recess. Contacts are secured in the insulative housing of the connector by deformable sections that minimize stress imposed on the housing, thereby reducing warpage. Solder resist areas are formed on central portions of the contacts to promote uniformity of solder volume. As a result of these features, substantial coplanarity of the BGA array along the mounting interface of the connector is achieved.

What is claimed is: 
     
       1. A method for placing an exterior conductive contact on an electrical connector having a base forming an exterior side and an interior side comprising the steps of: providing at least one recess on the exterior side of the base;   providing a conductive contact extending through the base from adjacent the interior side of the base to adjacent the recess on the exterior side of the base;   positioning a conductive element with at least a portion thereof in the recess provided on the exterior side of the base; and   securing the conductive element onto a region of the contact located generally furthest away from the interior side of the base while the conductive element is in the base.   
     
     
       2. The method of claim 1, wherein the securing step comprises fusing the conductive element onto the contact. 
     
     
       3. The method of claim 2, wherein the conductive element is fusible and the securing step comprises heating the conductive element to a temperature above its melting temperature. 
     
     
       4. A method as in claim 1, and further comprising the step of placing a paste material in the recess to a level to engage the conductive element. 
     
     
       5. A method as in claim 4, wherein the paste material is selected from the group consisting of solder paste, solder cream and solder flux. 
     
     
       6. The method of claim 4, wherein the paste is selected from a solder paste and a solder cream. 
     
     
       7. The method of claim 4, wherein the paste is a solder flux and the conductive contact is coated with a passivating agent. 
     
     
       8. A method as in claim 5, wherein the securing step comprises reflowing the paste to secure the conductive element on the contact. 
     
     
       9. A method as in claim 5, wherein the conductive element is formed of solder and the securing step comprising reflowing the solder paste and the solder. 
     
     
       10. The method of claim 1, wherein the conductive element is spherical. 
     
     
       11. The method of claim 10, wherein the recess is smaller in at least one transverse dimension than the largest transverse dimension of the conductive element. 
     
     
       12. The method of claim 4, wherein the recess has a depth, and said depth is from about 50 percent to about 200 percent of said at least one transverse dimension of the recess. 
     
     
       13. The method of claim 12, wherein the recess is a regular polygon in cross section. 
     
     
       14. The method of claim 13, wherein the polygon is a square. 
     
     
       15. The method of claim 4, wherein recess is circular in cross section. 
     
     
       16. The method of claim 9, wherein the contact extends into the recess by an amount which is from about 25 percent to about 75 percent of the depth of the recess. 
     
     
       17. The method of claim 6, wherein the recess is substantially filled with the paste. 
     
     
       18. The method of claim 9, wherein during said reflowing, the rise time between 180° C. and 200° C. is from about 10 seconds to about 100 seconds and fall time form 200° C. to 180° C. is from about 10 seconds to about 100 seconds, the base being positioned on a supporting substrate and the temperature being measured on said substrate. 
     
     
       19. The method of claim 9, wherein the solder is heated to above reflow for a period of time which is less than would result in the solder wicking onto the contact. 
     
     
       20. The method of claim 17, wherein when the solder is in a liquid phase, said solder has surface tension which restrains the solder from leaving the recess to wick onto the contact. 
     
     
       21. The method of claim 9, wherein the solder is heated according to a solder curve which has a maximum slope of from about 2° C./sec to about 15° C./sec. 
     
     
       22. The method of claim 18, wherein the base is heated to a peak temperature of about 185° C. to about 195° C. 
     
     
       23. The method of claim 9, wherein before reflow the solder is initially heated at a first rate after which said rate is decreased and after which said rate is increased until reflow temperature is reached. 
     
     
       24. The method of claim 18, wherein the solder curve has a minimum slope of from about -2° C./sec to about -15° C./sec. 
     
     
       25. The method of claim 9, wherein preheating is conducted for at least about one hour. 
     
     
       26. The method of claim 9, wherein heating to reflow temperature is conducted in a plurality of successive heating phases. 
     
     
       27. An exterior conductive contact placed on an electrical connector having a base forming an exterior side and an interior side by the steps of: providing at least one recess on the exterior side of the base;   providing a conductive contact extending through the base from adjacent the interior side of the base to adjacent the recess on the exterior side of the base;   positioning a conductive element with at least a portion thereof in the recess provided on the exterior side of the base; and   securing the conductive element onto a region of the contact located generally furthest away from the interior side of the base while the conductive element is in the base.   
     
     
       28. The method of claim 1, wherein the region of the contact resides entirely within the recess. 
     
     
       29. The method of claim 1, wherein the conductive element surrounds an end of the contact. 
     
     
       30. The method of claim 1, wherein the region is an angled tab.